U.S. patent application number 11/601430 was filed with the patent office on 2007-05-03 for braking device for a camshaft adjuster.
Invention is credited to Andreas Eichenberg, Matthias Gregor, Jens Meintschel.
Application Number | 20070095319 11/601430 |
Document ID | / |
Family ID | 34969315 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070095319 |
Kind Code |
A1 |
Eichenberg; Andreas ; et
al. |
May 3, 2007 |
Braking device for a camshaft adjuster
Abstract
In a braking device for a camshaft adjuster of an internal
combustion engine wherein the camshaft adjuster includes at least
two adjustment inputs, a respective braking element is provided for
each adjustment input to brake the respective adjustment input, the
braking elements being operable by an excitation coil arrangement,
which, depending on the direction of energization of an excitation
coil arrangement, subjects either the one or the other braking
element to magnetic flux for initiating braking of the respective
adjustment input.
Inventors: |
Eichenberg; Andreas;
(Chemnitz, DE) ; Gregor; Matthias; (Stuttgart,
DE) ; Meintschel; Jens; (Esslingen, DE) |
Correspondence
Address: |
KLAUS J. BACH
4407 TWIN OAKS DRIVE
MURRYSVILLE
PA
15668
US
|
Family ID: |
34969315 |
Appl. No.: |
11/601430 |
Filed: |
November 17, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP05/05228 |
May 13, 2005 |
|
|
|
11601430 |
Nov 17, 2006 |
|
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Current U.S.
Class: |
123/90.17 ;
123/90.15 |
Current CPC
Class: |
F01L 1/34409 20130101;
H02K 49/065 20130101 |
Class at
Publication: |
123/090.17 ;
123/090.15 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2004 |
DE |
10 2004 024 689.0 |
Claims
1. A braking device for a camshaft adjuster (10) of an internal
combustion engine, the camshaft adjuster having at least two
adjustment inputs (13, 14), with a respective braking element (31,
32) being provided for each adjustment input (13, 14) for braking
the respective adjustment input (13, 14), and means (42, 43, 44,
45, 36, 37, 38, 39, 48, 49) for subjecting either the one or the
other braking element (31, 32) to magnetic flux depending on a
direction of energization of an excitation coil arrangement
(35).
2. The braking device as claimed in claim 1, wherein one magnetic
circuit path (40, 41) is provided for each adjustment input (13,
14), with a magnetic flux path in the stator (39) common to both
magnetic circuit paths (40, 41).
3. The braking device as claimed in claim 2, wherein such an
excitation coil (36) common to both magnetic circuit path (40, 41)
is provided.
4. The braking device as claimed in claim 2, wherein a permanent
magnet (42, 43, 44, 45) is arranged in each magnetic circuit path
(40, 41).
5. The braking device as claimed in claim 4, wherein the permanent
magnets (42, 43) are arranged axially next to the excitation coil
(36).
6. The braking device as claimed in claim 4, wherein the braking
elements (31, 32) are in each case arranged axially next to the
excitation coil (36) and the respectively assigned permanent magnet
(42, 43).
7. The braking device as claimed in claim 4, wherein the permanent
magnets (44, 45) are arranged radially next to the excitation coil
(36).
8. The braking device as claimed in claim 1, wherein one excitation
coil (37, 38) is respectively provided for each magnetic circuit
path (40, 41).
9. The braking device as claimed in claim 8, wherein the excitation
coils (37, 38) are spaced apart axially.
10. The braking device as claimed in claim 8, wherein the current
flow through the excitation coils (37, 38) is controllable via
blocking elements (48, 49) connected electrically in series in each
case with the excitation coils (37, 38).
11. The braking device as claimed in claim 10, wherein the blocking
elements (48, 49) are structurally integrated with the excitation
coils (37, 38).
12. The braking device as claimed in claim 1, wherein shaft outputs
(17, 18) for subjecting adjustment inputs (13, 14) to braking
torque are arranged coaxially.
13. The braking device as claimed in claim 1, wherein the braking
elements (31, 32) are cylindrical and are in each case recessed in
an air gap (46, 47) extending in the circumferential direction of
the stator (39).
14. The braking device as claimed in claim 1, wherein the braking
elements (31, 32) are disk-shaped and are received in each case in
an air gap extending perpendicularly with respect to the axis of
symmetry of the stator (39).
Description
[0001] This is a Continuation-In-Part Application of pending
international patent application PCT/EP2005/005228 filed May 13,
2005 and claiming the priority of German patent application 10 2004
024 689.0 filed May 19, 2004.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a braking device for a camshaft
adjuster having at least two adjustment inputs each provided with a
braking element.
[0003] It is known to use a hysteresis brake in order to brake an
adjustment input of a camshaft adjusting device. If an excitation
coil of the hysteresis brake is energized, magnetic flux flows
through a rotating hysteresis element guided between pole
structures of a stator. The hysteresis element, which is moved by
the pole structure and is composed of magnetically half-hard
material, i.e. a material with a pronounced hysteresis loop in the
induction/magnetic field diagram (B/H diagram), is braked by a
continuous magnetic field reversal. A hysteresis brake of this type
for braking an adjustment input is known, for example, from DE 103
24 845 A1.
[0004] On the other hand, an adjusting device with two adjustment
inputs is described in DE 102004018942.0. In the case of an
adjusting device of this type with more than one adjustment inputs,
each adjustment input has to be able to be braked. If a hysteresis
brake is therefore provided for each adjustment input, a
considerable amount of space is required and a complicated control
of the adjusting device and of the braking device is needed.
[0005] It is the object of the present invention to provide a
braking device for an adjusting device with at least two adjustment
inputs, which braking device is as highly compact and can be
controlled in a simple manner.
SUMMARY OF THE INVENTION
[0006] In a braking device for a camshaft adjuster of an internal
combustion engine wherein the camshaft adjuster includes at least
two adjustment inputs, a respective braking element is provided for
each adjustment input to brake the respective adjustment input, the
braking elements being operable by an excitation coil arrangement,
which, depending on the direction of energization of an excitation
coil arrangement, subjects either the one or the other braking
element to magnetic flux for initiating braking of the respective
adjustment input.
[0007] With such a braking device, the contactlessly operating
brake preferably operates with electromagnetic induction; that is
it is a hysteresis brake with a braking element in the form of a
rotatable ring member or rotatable disk. By means of a magnetic
flux introduced into the respective braking element via a pole
structure of a stator, a braking torque can be generated in a
specific manner in an individual braking element and the adjustment
input assigned to the braking element can be braked. The means
which can be used are preferably permanent magnets in the manner of
a flux valve for the magnetic flux, the permanent magnets
interacting in particular with a single excitation coil. Also, two
excitation coils may be provided which interact in a suitable
arrangement with the common stator, the magnetic flux being guided
along different, defined paths in the stator as a function of the
direction of energization. Upon appropriate energization, the
magnetic flux flows through the one braking element, the braking
torque of which rises sharply with increasing electric current
applied to the excitation coil device up to a high maximum torque.
When the energization polarity is reversed, the flow
correspondingly passes through the other braking element. The
braking elements are expediently braking elements which are
separated from one another and are arranged on a respective
rotating support structure, in particular rings or disks consisting
of magnetically half-hard material, and forming a type of tandem
hysteresis brake.
[0008] In particular in the case of an adjusting device designed as
a passive, driveless four-shaft gear mechanism, as described in DE
10 2004 018 942.0, in order to adjust the device in one direction,
the first adjustment input can be braked and the second adjustment
input can be released, and, in order to adjust the device in the
opposite direction, the second adjustment input can be braked and
the first adjustment input can be released.
[0009] According to the invention, the braking elements, which are
annular bands (rings) or disks, can be activated as a function of
each other. This is advantageous in particular for the
abovementioned adjusting device, since, in the case of the latter,
an independent control of its two braking elements is not
necessary.
[0010] Preferably, a partial magnetic circuit is provided per
adjustment input, with a stator common to the partial magnetic
circuits. This advantageously results in the braking torque being
distributed to the individual braking elements during positive and
during negative energization of the excitation coil device, so that
the activation of the brake is simplified and the construction
space required is reduced. Furthermore, the braking device is
cost-effective; the simplified design permits the used of the same
components to generate the braking torque in either or both braking
elements.
[0011] In a first preferred refinement, a common excitation coil is
provided. A permanent magnet is preferably arranged in each
magnetic pitch circle, with the permanent magnets advantageously
being arranged axially next to the excitation coil. It is
furthermore advantageous if the braking elements are in each case
arranged axially next to the excitation coil and the assigned
permanent magnet. This design makes it possible to keep the outside
diameter of the braking device small. The magnetic flux is used by
either of the two braking elements. The permanent magnets with
secondary magnetic flux act as valves for the magnetic flux and
only allow the latter to pass in each case in one direction.
Depending on the direction of energization of the excitation coil,
this forces the magnetic flux onto different paths within the
braking device. If one braking element in each case is arranged in
a different path of the magnetic flux, as a function of the
energization one braking element in each case, the polarity of
which corresponds to a blocking direction for the current magnetic
flux, can block the magnetic flux while the magnetic flux flows
through the other braking element. At a certain excitation value,
the flux is directly related to the torque generated in the
respective braking element.
[0012] In a second preferred refinement, the permanent magnets are
arranged radially next to the excitation coil. This manner of
construction is distinguished by a particularly small axial
construction length of the braking device. Depending on the
direction of energization of the excitation coil, the magnetic flux
is either impeded or assisted by the respective permanent magnet.
Thus, a braking torque is only produced in the braking element
through which the flow passes while no braking torque is produced
in the braking element through which the flow does not pass. An
output shaft of the braking device, which output shaft is assigned
to the braking element through which the flow passes, or the
adjustment input, which is connected thereto, of the adjusting
device is accordingly braked.
[0013] In a further preferred refinement, one excitation coil is
respectively provided per magnetic pitch circle. The excitation
coils replace the permanent magnets as valves for the magnetic
flux. The excitation coils are preferably spaced apart axially and
are accommodated in a common stator. Depending on which excitation
coil of the excitation coil device is energized, the flow passes in
each case only through the corresponding braking element of the
respective magnetic pitch circle, and the magnetic flux for each
excitation coil is guided on a different path in the stator.
[0014] In an advantageous development, the current flow through the
excitation coils is controlled via blocking elements connected
electrically in series in each case with the excitation coils. The
blocking elements are preferably diodes or switching circuits with
a blocking and a passage direction. The braking device can be
activated by means of just two electric supply cables, which is
cost-effective and has a very advantageous effect on the weight and
volume of the braking device. It is particularly space-saving to
structurally integrate the blocking elements with the excitation
coils.
[0015] The braking elements can be cylindrical in the form of
annular bands or rings which are in each case guided in an air gap
extending in the circumferential direction of the stator and
parallel to the axis of symmetry. Alternatively, the braking
elements can be disk-shaped and can in each case be guided in an
air gap extending perpendicularly with respect to the axis of
symmetry of the stator.
[0016] The invention will become more readily apparent from the
following description with an exemplary embodiment with reference
to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 shows schematically of a preferred four-shaft gear
mechanism for adjusting the phase position of a camshaft with two
adjustment inputs,
[0018] FIG. 2 shows diagrammatically a profile of a magnetic flux
as a function of an excitation current for one braking element in
each case per adjustment input,
[0019] FIG. 3 shows, in section, a first preferred embodiment of a
braking device according to the invention with permanent magnets
serving as valves for a magnetic flux,
[0020] FIG. 4 shows a profile of magnetic field lines in the
arrangement of FIG. 3,
[0021] FIG. 5 shows a calculated profile of the magnetic flux or of
a braking torque in two braking elements as a function of the
excitation current for the arrangement of FIG. 3,
[0022] FIG. 6 shows, in section, an alternative preferred
embodiment of a braking device with permanent magnets serving as
valve for the magnetic flux,
[0023] FIG. 7 shows a profile of magnetic field lines in the
arrangement of FIG. 6,
[0024] FIG. 8 shows a calculated profile of the magnetic flux or of
a braking torque in two braking elements as a function of the
excitation current for the arrangement of FIG. 6,
[0025] FIG. 9 shows, in section, another preferred embodiment of a
braking device according to the invention with two excitation coils
and a stator yoke serving as the valve for a magnetic flux,
[0026] FIG. 10 shows a profile of magnetic field lines in the
arrangement in FIG. 9,
[0027] FIG. 11 shows a calculated profile of the magnetic flux or
of a braking torque in two braking elements as a function of the
excitation current for the arrangement of FIG. 9, and
[0028] FIG. 12 shows a preferred electric circuit for the
activation, as a function of the direction of energization, of in
each case one of the excitation coils in the arrangement according
to FIG. 9.
DESCRIPTION OF PARTICULAR EMBODIMENTS OF THE INVENTION
[0029] In the figures, identical elements or elements which remain
essentially the same are numbered by the same reference numbers. In
the figures, the terms "radially" and "axially" relate in each case
to an orientation with respect to an axis of symmetry or axis of
rotation 50.
[0030] A preferred, particularly compact adjusting device 10 in the
form of a four-shaft gear mechanism, in accordance with DE 10 2004
018 942.0 is shown schematically in FIG. 1. The adjusting device 10
has a first and a second adjustment input 13, 14 for two partial
gear mechanisms 11, 12, an input for a drive element, which is in
the form of a drive wheel 15, and an output for driving a camshaft
16. For adjustment in the one direction, the first adjustment input
13 is braked and the second adjustment input 14 is released; for
adjustment in the opposite direction, the second adjustment input
14 is braked and the other adjustment input 13 is released.
[0031] The braking device according to the invention operates in
accordance with the principle of a hysteresis brake, with one
braking element in each case being provided for braking the
respective adjustment input 13, 14. In the ideal case, a profile of
the magnetic flux and, correspondingly, of the braking torque over
an electric excitation current for each braking element is such
that, in the first direction of energization of an excitation coil
device, the magnetic flux flows through the first braking element,
and, in the opposite direction of energization, the magnetic flux
flows through the second braking element for generating a
corresponding braking torque.
[0032] FIG. 2 shows an idealized profile of the flux .PHI.(I) or of
the braking torque M(I) as a function of the excitation current I.
Curve 20 shows a steep rise in the flux .PHI.(I) and of the braking
torque M(I) as the excitation current I of the first braking
element rises while, given the same direction of energization, the
second braking element makes virtually no contribution, as can be
seen at curve 21. If the direction of energization is reversed, the
braking torque M(I) is supplied by the second braking element
(curve 21 with negative excitation current I). A profile of the
curves 20, 21 that is as steep as possible is sought here.
[0033] A first preferred refinement of the braking device according
to the invention is shown in a sectional illustration in FIG. 3.
Details of the adjusting device itself are not illustrated. The
braking device 30 contains two braking elements 31, 32, in the form
of annular bands, an excitation coil device with an excitation coil
36 and two permanent magnets 42, 43. These elements are arranged
within a stator 39 in such a manner that they form two magnetic
circuit paths 40, 41. The stator 39 is rotationally symmetrical
with respect to an axis of symmetry which coincides with the axis
of rotation 50 of two shaft outputs 17, 18.
[0034] A support 33 is arranged at the first shaft output 17, at
its end facing the input of the braking device 30, which support,
on its circumference, carries the first braking element 31, which
is designed as a band. A support 34 is arranged at the second shaft
output 18, at its end facing the output of the braking device 30,
which carries a second braking element 32, in the form of an
annular band. The shaft outputs 17, 18 are arranged coaxially and
are connected to the coaxially designed adjustment inputs 13, 14
(FIG. 1).
[0035] The braking device 30 is formed in a rotationally
symmetrical manner with respect to the axis of rotation 50. The
braking elements 31, 32, which are in the form of annular bands,
respectively are received in air gaps 46 and 47 arranged on the
opposite axial ends of the stator 39, with a pole structure
including magnetic poles, which are disposed opposite each other,
being arranged in the radial direction on both sides of the air
gaps 46, 47. The air gaps 46, 47 extend parallel to the axis of
rotation 50. An excitation coil 36 which is wound coaxially with
respect to the axis of rotation 50 is arranged in a cavity 60 of
the stator 39. In the axial direction upstream and downstream of
the coil winding, the cavity 60 has a respective end portion in
which in each case one of the permanent magnets 42, 43 is arranged.
The permanent magnets 42, 43 are magnetized in the same direction.
Axially adjacent to the permanent magnets 42, 43, respective
further cavities 63, 64, are provided in the stator 39 in
communication with the air gaps 46, 47. The air gaps 46, 47 improve
the magnetic field distribution by focusing the magnetic flux in
the region of the braking elements 31, 32. Depending in each case
on the direction of energization of the excitation coil 36, the
magnetic flux passes essentially only through one of the braking
elements 31 or 32. On the circumferential surface of the braking
device 30, the stator 39 has an output part 65 which, at its
opposite axial ends, is provided with a part of the pole structure
51, 52 and which covers the cavities 60, 63, 64 and air gaps 46, 47
of the stator 39. In the stator 39, elements, such as the permanent
magnets 42, 43, the coil 36 and the braking elements 31, 32, are
arranged axially next to one another, which results in an
advantageously small outside diameter of the braking device 30. The
permanent magnets 42, 43 with secondary magnetic flux serve as
valves which allow the flux .PHI.(I) only to pass in one direction,
as a result of which locally different distributions of flux occur
for different directions of energization of the excitation coil
36.
[0036] For the function of the individual elements, reference is
made below to the preceding figures in order to avoid unnecessary
repetitions.
[0037] A profile of magnetic field lines of the arrangement of FIG.
3 is illustrated in FIG. 4. Only one side of the field profile is
illustrated; the arrangement is rotationally symmetrical with
respect to the axis of symmetry or axis of rotation 50. The
direction of energization of the excitation coil 36 is selected in
such a manner that the second permanent magnet 43 blocks and the
first permanent magnet 42 assists the magnetic flux, with the
result that the flow passes through the second magnetic circuit
path 41. As a result, the flow passes through the second braking
element 32, and a braking torque M(I) is produced by the
latter.
[0038] FIG. 5 shows a calculated profile of the magnetic flux
.PHI.(I) and the braking torque M(I) as a function of the
excitation current I through the excitation coil 36 for both
braking elements 31, 32. Curve 22 shows the profile for the first
braking element 31, curve 23 shows the profile for the second
braking element 32. Without excitation current I through the
excitation coil 36, magnetic flux .PHI.(I) is produced only by the
two relatively weak permanent magnets 42, 43. The magnetic flux
.PHI.(I) is identical at both braking elements 31, 32 and therefore
also produces the same braking torque M(I). The curves 22, 23 of
the flux .PHI.(I) and of the braking torque M(I) have a steep
profile and advantageously achieve high maximum values. If the
four-shaft gear mechanism mentioned at the beginning is subjected
to the same braking torque M(I) at both adjustment inputs 13, 14,
no phase adjustment takes place and the phase position of the
camshaft relative to the crankshaft remains unchanged.
[0039] A small construction length can be obtained with the braking
device 30 as illustrated schematically in FIG. 6. For the
description and function of the individual elements, reference is
made to the preceding figures. Starting from a cavity 60, in which
an excitation coil 36 is arranged, which includes a winding wound
in the circumferential direction, permanent magnets 44, 45 are
arranged in end portions which extend radially away from the cavity
60, said permanent magnets being installed coaxially with respect
to the axis of rotation 50 and being spaced apart axially from each
other opposite. The axial end portions of the magnets 44, 45 in
each case coincide with the axial ends of the cavity 60. The
permanent magnets 44, 45 are magnetized in the axial direction, the
two permanent magnets 44, 45 being magnetized in opposite
directions. Two cavities 63, 64 extend away from the end portions
in the radial direction toward an outer part 65 which, at its axial
ends, forms a part of pole structures 51, 52 and covers the air
gaps 46, 47 and the cavities 63, 64 of the stator 39.
[0040] An associated flux line profile is explained in FIG. 7. The
direction of energization is selected in such a manner that the
first permanent magnet 44 blocks and thus forces the magnetic flux
into the first braking element 31 while virtually no flow passes
through the second braking element 32. The direction of
energization is selected in such a manner that the flow passes
through the first magnetic circuit path 40. When the direction of
current through the excitation coil 36 is reversed, the conditions
are reversed.
[0041] FIG. 8 shows a calculated profile of the magnetic flux
.PHI.(I) and of the braking torque M(I) as a function of the
excitation current I through the excitation coil 36. Curve 24 shows
the profile for the first braking element 31, curve 25 shows the
profile for the second braking element 32. The curves 24, 25 of the
flux .PHI.(I) and of the braking torque M(I) have a steep profile
and advantageously achieve high maximum values.
[0042] FIG. 9 shows another embodiment of the invention. Instead of
permanent magnets acting as flux valves, an excitation coil device
with two excitation coils 37, 38, which are arranged in cavities
61, 62 of the stator 39, are provided for controlling a path of the
magnetic flux .PHI.(I) in a stator 39. The excitation coils 37, 38
are arranged essentially on the same diameter coaxially about an
axis of rotation 50 of the braking device 30 and spaced apart
axially. The windings of the excitation coils 37, 38 extend in the
circumferential direction of the stator 39. On its axial end sides,
the stator 39 has air gaps 46, 47 which extend in the axial
direction parallel to the axis of rotation 50 and in which a
respective braking element 31, 32, in the form of annular bands,
are accommodated. The braking elements 31, 32 have a diameter which
is slightly larger than the outside diameter of the excitation
coils 37, 38. The excitation coils 37, 38 adjoin the braking
elements 31, 32 in an axially close-fitting manner. In this
embodiment, energization of one of the excitation coils 37 or 38
causes the magnetic flux .PHI.(I) to be directed through, in each
case, just one braking element 31 or 32. The excitation coils 37,
38 together with their assigned braking elements 31, 32 form
magnetic circuit paths 40, 41. The flux paths in the stator 39 are
determined solely by the stator 39 and permanent magnets are not
required here. If only the first excitation coil 37 is energized,
then the magnetic flux also only passes through the first braking
element 31. If only the second excitation coil 38 is energized, the
flow only passes through the second braking element. FIG. 10 shows
the associated flux profile when only the first excitation coil 37
is energized. As in the case of the preceding refinements of the
invention, this arrangement also shows an advantageous steep
increase in the magnetic flux through the respective braking
elements 31, 32 through which the flow passes, when the excitation
current I rises. This can be seen in FIG. 11 with reference to the
curve 27 for the first braking element 31 and curve 26 for the
second braking element 32. The calculated magnetic flux .PHI.(I)
and the braking torque M(I) are plotted here as a function of the
excitation current I through the particular excitation coil 37 or
38.
[0043] Simple activation of the braking device 30 by means of two
electric supply lines is possible with a circuit 53 which is
sketched in FIG. 12. The circuit 53 is arranged between an
activating means (not illustrated) and the braking device 30. An
electric voltage U is applied across poles 54 and 55 which supply a
voltage to a first circuit branch with a first excitation coil 37
and a first blocking element 48, which is connected electrically in
series therewith and is a blocking diode, and, parallel thereto, a
second circuit branch with a second excitation coil 38 with a
second blocking element 49, which is connected electrically in
series therewith and is a blocking diode. The two blocking elements
48, 49 are connected in such a manner that one blocks when the
other is switched into the pass-through direction. Accordingly, in
a given direction of energization, only one excitation coil 37 or
38 can be energized because the blocking element 49 or 48 in the
other circuit branch forms a block. It is particularly advantageous
to integrate this circuit directly into the braking device 30.
[0044] The refinements according to the invention can be realized
both with braking elements 31, 32 in the form of annular bands and
with braking elements 31, 32 in the form of as disks. It is also
possible to provide one of the braking elements 31, 32 in the form
of a disk and the other in the form of an annular band.
[0045] A preferred camshaft adjusting device includes a four-shaft
gear mechanism with two coaxial adjustment inputs, and also
includes the braking device 30 according to the invention with two
coaxial shaft outputs 17, 18.
* * * * *